/*
* Copyright 1997-2005 Sun Microsystems, Inc. All Rights Reserved.
* DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
*
* This code is free software; you can redistribute it and/or modify it
* under the terms of the GNU General Public License version 2 only, as
* published by the Free Software Foundation. Sun designates this
* particular file as subject to the "Classpath" exception as provided
* by Sun in the LICENSE file that accompanied this code.
*
* This code is distributed in the hope that it will be useful, but WITHOUT
* ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
* FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
* version 2 for more details (a copy is included in the LICENSE file that
* accompanied this code).
*
* You should have received a copy of the GNU General Public License version
* 2 along with this work; if not, write to the Free Software Foundation,
* Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
*
* Please contact Sun Microsystems, Inc., 4150 Network Circle, Santa Clara,
* CA 95054 USA or visit www.sun.com if you need additional information or
* have any questions.
*/
package javax.swing.undo;
import javax.swing.event.*;
/**
* An <code>UndoableEdit</code> represents an edit. The edit may
* be undone, or if already undone the edit may be redone.
* <p>
* <code>UndoableEdit</code> is designed to be used with the
* <code>UndoManager</code>. As <code>UndoableEdit</code>s are generated
* by an <code>UndoableEditListener</code> they are typically added to
* the <code>UndoManager</code>. When an <code>UndoableEdit</code>
* is added to an <code>UndoManager</code> the following occurs (assuming
* <code>end</code> has not been called on the <code>UndoManager</code>):
* <ol>
* <li>If the <code>UndoManager</code> contains edits it will call
* <code>addEdit</code> on the current edit passing in the new edit
* as the argument. If <code>addEdit</code> returns true the
* new edit is assumed to have been incorporated into the current edit and
* the new edit will not be added to the list of current edits.
* Edits can use <code>addEdit</code> as a way for smaller edits to
* be incorporated into a larger edit and treated as a single edit.
* <li>If <code>addEdit</code> returns false <code>replaceEdit</code>
* is called on the new edit with the current edit passed in as the
* argument. This is the inverse of <code>addEdit</code> —
* if the new edit returns true from <code>replaceEdit</code>, the new
* edit replaces the current edit.
* </ol>
* The <code>UndoManager</code> makes use of
* <code>isSignificant</code> to determine how many edits should be
* undone or redone. The <code>UndoManager</code> will undo or redo
* all insignificant edits (<code>isSignificant</code> returns false)
* between the current edit and the last or
* next significant edit. <code>addEdit</code> and
* <code>replaceEdit</code> can be used to treat multiple edits as
* a single edit, returning false from <code>isSignificant</code>
* allows for treating can be used to
* have many smaller edits undone or redone at once. Similar functionality
* can also be done using the <code>addEdit</code> method.
*
* @author Ray Ryan
*/
public interface UndoableEdit {
/**
* Undo the edit.
*
* @throws CannotUndoException if this edit can not be undone
*/
public void undo() throws CannotUndoException;
/**
* Returns true if this edit may be undone.
*
* @return true if this edit may be undone
*/
public boolean canUndo();
/**
* Re-applies the edit.
*
* @throws CannotRedoException if this edit can not be redone
*/
public void redo() throws CannotRedoException;
/**
* Returns true if this edit may be redone.
*
* @return true if this edit may be redone
*/
public boolean canRedo();
/**
* Informs the edit that it should no longer be used. Once an
* <code>UndoableEdit</code> has been marked as dead it can no longer
* be undone or redone.
* <p>
* This is a useful hook for cleaning up state no longer
* needed once undoing or redoing is impossible--for example,
* deleting file resources used by objects that can no longer be
* undeleted. <code>UndoManager</code> calls this before it dequeues edits.
* <p>
* Note that this is a one-way operation. There is no "un-die"
* method.
*
* @see CompoundEdit#die
*/
public void die();
/**
* Adds an <code>UndoableEdit</code> to this <code>UndoableEdit</code>.
* This method can be used to coalesce smaller edits into a larger
* compound edit. For example, text editors typically allow
* undo operations to apply to words or sentences. The text
* editor may choose to generate edits on each key event, but allow
* those edits to be coalesced into a more user-friendly unit, such as
* a word. In this case, the <code>UndoableEdit</code> would
* override <code>addEdit</code> to return true when the edits may
* be coalesced.
* <p>
* A return value of true indicates <code>anEdit</code> was incorporated
* into this edit. A return value of false indicates <code>anEdit</code>
* may not be incorporated into this edit.
* <p>Typically the receiver is already in the queue of a
* <code>UndoManager</code> (or other <code>UndoableEditListener</code>),
* and is being given a chance to incorporate <code>anEdit</code>
* rather than letting it be added to the queue in turn.</p>
*
* <p>If true is returned, from now on <code>anEdit</code> must return
* false from <code>canUndo</code> and <code>canRedo</code>,
* and must throw the appropriate exception on <code>undo</code> or
* <code>redo</code>.</p>
*
* @param anEdit the edit to be added
* @return true if <code>anEdit</code> may be incorporated into this
* edit
*/
public boolean addEdit(UndoableEdit anEdit);
/**
* Returns true if this <code>UndoableEdit</code> should replace
* <code>anEdit</code>. This method is used by <code>CompoundEdit</code>
* and the <code>UndoManager</code>; it is called if
* <code>anEdit</code> could not be added to the current edit
* (<code>addEdit</code> returns false).
* <p>
* This method provides a way for an edit to replace an existing edit.
* <p>This message is the opposite of addEdit--anEdit has typically
* already been queued in an <code>UndoManager</code> (or other
* UndoableEditListener), and the receiver is being given a chance
* to take its place.</p>
*
* <p>If true is returned, from now on anEdit must return false from
* canUndo() and canRedo(), and must throw the appropriate
* exception on undo() or redo().</p>
*
* @param anEdit the edit that replaces the current edit
* @return true if this edit should replace <code>anEdit</code>
*/
public boolean replaceEdit(UndoableEdit anEdit);
/**
* Returns true if this edit is considered significant. A significant
* edit is typically an edit that should be presented to the user, perhaps
* on a menu item or tooltip. The <code>UndoManager</code> will undo,
* or redo, all insignificant edits to the next significant edit.
*
* @return true if this edit is significant
*/
public boolean isSignificant();
/**
* Returns a localized, human-readable description of this edit, suitable
* for use in a change log, for example.
*
* @return description of this edit
*/
public String getPresentationName();
/**
* Returns a localized, human-readable description of the undoable form of
* this edit, suitable for use as an Undo menu item, for example.
* This is typically derived from <code>getPresentationName</code>.
*
* @return a description of the undoable form of this edit
*/
public String getUndoPresentationName();
/**
* Returns a localized, human-readable description of the redoable form of
* this edit, suitable for use as a Redo menu item, for example. This is
* typically derived from <code>getPresentationName</code>.
*
* @return a description of the redoable form of this edit
*/
public String getRedoPresentationName();
}